DNA prepared from chagasic patientsïsera were amplified by the Polymerase Chain Reaction (PCR) using oligonucleotide primers which anneal specifically to a highly repetitive sequence of Trypanosoma Cruzi nuclear DNA. Sample from both acutely and chronically infected patients yielded positive results by this method. No significant difference was observed when either whole blood or serum sample of the patients were used. These results indicate that serum instead of whole blood sample could be used for PCR-based detection of T. Cruzi in field studies without the of applying any special chemical treatment of the specimens. This would represent a considerable advantage due to the easier handling and transportation of serum as compared with whole blood samples, especially in tropical climates